A robotic space probe nearly 900m miles (1.5bn kilometres) from Earth has turned its gaze away from Saturn and its entourage of moons to take a rare picture of its home planet.

The resulting image shows Earth as a very small, blue-tinged dot – paler and tinier than in other photos – overshadowed by the gas giant Saturn's rings in the foreground.

"We can't see individual continents or people in this portrait of Earth, but this pale blue dot is a succinct summary of who we were on July 19," Linda Spilker, Cassini spacecraft lead scientist at the Jet Propulsion Laboratory in Pasadena, California, said in a statement.

Cassini took the picture on Friday, the same day Nasa's Mercury-orbiting Messenger probe also photographed Earth. In that picture, Earth and the moon take up less than a pixel, but appear large because they are overexposed.

"That images of our planet have been acquired on a single day from two distant solar system outposts reminds us of this nation's stunning technical accomplishments in planetary exploration," Messenger lead scientist Sean Solomon, with Columbia University in New York, said in a statement.

"The whole event underscores for me our 'coming of age' as planetary explorers," said astronomer Carolyn Porco, who oversees the Cassini imaging team at the Space Science Institute in Boulder, Colorado.

Usually, spacecraft in the far reaches of the solar system don't look back towards Earth to avoid damaging their instruments by direct sunlight. Last week, the sun was temporarily blocked relative to Cassini's line of sight, allowing the pictures to be taken.